Transparent metal fabricating lubricant



Patent ecl Aug. 30, 1949 TRANSPARENT METAL FABRICATIN G LUBRICANT Arnold J. Morway, Clark, and Hollis .L. Leland,

Cranford, N. 3., assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application April 5, 1947,

Serial No. 739,654 r 5 Claims. 1

The present invention relates to a transparent metal fabricating lubricant. More particularly it relates to cutting oils and the like comprising light colored mineral oils of lubricating grade to which are added extreme pressure agents capable of lubricating under the extreme pressures encountered in machining operations and which also have the desirable characteristics of being light colored and fairly transparent so as not to obscure the operation of the cutting tool or analogous machine element.

In the past metal fabricating lubricants have consisted generally of sulfurized or sulfur chloride treated mineral oils with or without sulfurized fatty oils and/or soaps and the like. Some cutting oils have consisted largely of fatty saponifiable oils sulfurized suitably and used alone or in combination with relatively small amounts of mineral oil in order that high sulfur content might be obtained. When sulfurized mineral oil 'alone has been employed it usually has been dark 'or black in color.

This is true because the clear light colored oils are not suitable for reacting with sulfur to obtain satisfactory extreme pressure properties combined with stability. Also, when fatty oils have been employed, these have usually turned dark at the elevated sulfurization temperatures so that they are relatively opaque. Obviously, dark and relatively opaque oils, whether fatty oils or mineral oils, are objectionable when fine machining operations are being undertaken since they obscure the work from the operator. It therefore, an object of our invention to prepare a transparent cutting or metal fabricating oil base by the sulfurization of an unhydrogenated or partially hydrogenated methyl or ethyl ester of abietic acid and to so treat the compound as to prevent mechanical separation, precipitation or other degeneration or degradation of quality.

A cutting oil using a sulfurized methyl ester of an abietic acid has been known in the prior art but has not been entirely satisfactory because during storage a certain amount of decomposition appears to occur. As a result, a precipitate forms and settles out of the. oil, carrying with it at least a large part of the sulfur.

The precipitate appears to be some reaction product or complex of sulfur and the abietic acid ester. A typical analysis 'of this precipitate shows that it contains sulfur to the extent of about 54%, more or less. Precipitation of this material is obviously undesirable since it materiallyreduces the extreme pressure efficiency of the lubricant. V 7

We have discovered that this undesirable precipitation in oils of the abietic acid ester type can be quite fully and satisfactorily eliminated by the employment of certain oil soluble metallic sulfonates in combination with the abietic acid ester during sulfurization. It appears to be particularly important to combine the sulfonates with the ester prior to sulfurization. We have found that addition of the sulfonates after sulfurization of the abietic acid ester is not effective and. does not prevent the precipitation from occurring- Commercial methyl esters of abietic acid are available on the market and are sold under various trade names. One of these is the methyl ester of abietic acid and another appears to be themethyl ester of dihydroabietic acid or of ftetrahydroabietic acid. The preparation of the .latter type of esters is shown in U. S. Patents 1,877,179 and 1,944,241, issued to I. W. Humphrey. The structural formula of the first of these comf pounds appears to be as follows:

CH; 0 0 0 CH3 "esters such as ethyl, propyl and isopropyl may likewise be used if desired. Thus esters prepared by using the lower alcohols, particularly those. having from 1 to 3 carbon atoms, are sati'sfactory. The methyl ester is preferred at prescut" because of its ready availability. Y

While various oil soluble metallic. sulfonates are suitable, such as potassium and calcium sulfonates and the like, we prefer to use the sodium sulfonates as these are readily available, being .formedrby the simple reaction of sodium hydrox- 3 ide with mahogany sulfonic acids obtained from the treatment of crude oils with strong sulfuric acid. A typical formula of our improved metal Methyl ester of abietic acid 77.30

Sodium sulfonates (70% soaps) 4.52 Light colored low cold test Coastal mineral oil (40 seconds viscosity at 210 F.) 9.09

The ester and sodium sulfonates are heated to about 300 F. in a vessel equipped with a means for mechanical agitation. The sulfur is added over a period of five minutes or the sulfur can be metered into the ester in a molten state. The temperature is rapidly raised to a suitable temperature, for example 350 F., and held at this temperature until the sulfur is completely reacted with the ester. Sulfurization temperatures may be as low as about 250 F. but temperatures of 300 F. to 400 F. are preferred. When the suliurization is completed, generally within 50 minutes, the temperature is quickly lowered from the rapid reaction zone by quenching with the cold mineral oil or by passage through a suitable heat exchanger. The base may now be mixed in a suitable concentration, preferably about 10%, with mineral oil to obtain a finished transparent cutting oil, or may be packaged and stored as a base for future finishing.

In general, a suitable fabricating lubricating oil will consist of '75 to 99% mineral oil to which is added 25 to 1% of the compound described above. The additive may be marketed commercially fOr combination with mineral oil by the customer and in such cases it will contain only a small amount of oil, for example, only that amount that was needed for quenching at the end of the sulfurization reaction. On the other hand, the oil and additive may be combined at the refinery, in which case mineral oil will normally be the principal constituent of the composition.

Hence the percentage composition may vary from 5 to about 99% mineral oil, depending on Whether the concentrated additive or the final oil, as actually used in metal fabrication, is being prepared. In the case of the concentrate, sulfur content may be as much as 20%, whereas it may be as low as 0.5% or less in the finished product. Likewise the methyl ester of ab-ie'tic acid may vary from as much as 85% in the concentrate to as little as about 1% or slightly iess in the finished product. As a rule, however, at least 5% will be used. In a similar manner the metal sulfonate, which is preferably the sodium mahogany sulfonate, although other oil-soluble sulfonates such as potassium, lithium, calcium, strontium, barium, aluminum and zinc sulfonates may be used, will vary from as much as in the concentrate to as little as 0.2% or less in the finished product. The figures for the various materials used in dilute oil solution may of course vary considerably, depending in a large measure on the quantity of additive used in the final oil.

Instead of mineral oil, lard oil and other known animal and vegetable oils maybe used to replace part or all of the mineral oil. As suggested above, however, it is generally considered desirable to avoid blackening of these oils; hence, they are preferably not added to the h'otreaction product of sulfurization. I

'The amount of oil in the concentrate obviously may be varied between rather wide limits. A suitable concentrate composition may consist essentially of 5 to 20% (or parts by weight) sulfur, 40 or 50% and up to or of a methyl abietate or hydroabietate ester such as those described above, and 2 to 15% metal sulfonate, the metal being selected from the group of metals consisting of the alkali metals, alkaline earth metals, zinc, and aluminum.

Test data actually obtained in connection with working out details of our invention are shown below.

Precipitation data Material Time for Precipitation to show after blending base in a 10% concentration in mineral oil Suliurized methyl ester of abietic acid (as described without sulfonates present).

Sulfurized ester as above (Same concentration of sulfonates as given but added after the sulfurization).

Sulfurized ester as above (Sulfurized with sulfonate present) Large precipitation of solid material after less than one week standing at room temperature.

No preeipitaton after 3 months standing at room temperature or 0 1'. with warming to room temperature once a week and allowing to stand for 25 hours.

Inspection data. on finished fabricating oil of present invention 10% base dissolved in 90% low cold test mineral oil (38.0 vis./2l0 F.)

Rough cut: Turn "'thread 0.013".

Fin-ish'cut: Skin out.

The performance of the oil described in this application was entirely satisfactory and performed comparably with a premium non-transparent black fabricating oil. It 'had the obvious and important advantage of transparency. The

tool life could not be judged exactly becausesand holes were present in "the castings; however, over the test period, the tool life averaged about the same as with a'likeperi'od on the premium grade black opaque oil of the prior art. The finish of the Work was slightly improved over that with the black oil. The machine tool operator who tested the two products was particularly pleased with lack of odor and the transparency of the oil. The oil did not darken after continuous'us'e over a period of one m'onth-andequally satisfacto'ry finish, tool life, and machine speed were obtained at the end of the test period as at'ithe start.

'1. A light colored metal fabricating composition consisting essentially of a light colored mineral base lubricating oil containin 1 to 25%, based on the total composition, of a concentrate obtained by combining light mineral oil with 5 to 20 parts by weight of sulfur, 40 to 85 parts of a C1 to C3 alkyl ester of abietic acid, and 2 to parts of a. metal sulfonate, heated to a. temperature of 300 to 400 F. until the sulfur is substantially completely reacted with the ester.

2. A lubricant as described in claim 1 wherein said ester is methyl abietate.

3. A lubricant as described in claim 1 wherein said ester is methyl hydroabietate.

4. A transparent cutting oil consisting essentially of 80 to 99% light colored mineral oil, containing to 1% of the reaction product obtained by combining 40 to 85 parts by weight of a methyl ester of abietic acid and 2 to 15 parts of a metal sulfonate, agitating said ester and sulfonate and heating the agitated mixture with 5 to 20 parts of sulfur to 300 to 400 F., and quenching with cold mineral oil.

5. A lubricating composition consisting essentially of a light colored mineral base lubricating oil containing 1 to by weight of a load carry- 25 ing additive obtained by combining the following ingredients in the weight proportions indicated:

Per cent Flowers of sulfur 9.09 Methyl ester of abietic acid 77.30 Sodium sulfonates (70% soaps) 4.52 Light colored low cold test Coastal mineral oil seconds viscosity at 210 F.) 9.09

said additive being prepared by combining and heating together said ester and sulfonate to a temperature of about 300 F., then adding said sulfur and cooking at a temperature of 300- 400 F. until sulfurization is completed, and thereafter quenching said cooked ingredients in said low cold test oil.

ARNOLD J. MORWAY.

HOLLIS L. LELAND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,220,843 Johnson Nov. 5, 1940 2,271,947 Morway Feb. 3, 1942 2,289,438 Knowles July 14, 1942 2,418,894 McNab Apr. 15, 1947 

